Cannabis in Illinois is legal for both medical and adult use.

Illinois legalized cannabis for medical use in 2013 through the Compassionate Use of Medical Cannabis Program Act. Illinois went on to legalize the  adult use of cannabis in 2019 through the Illinois Cannabis Regulation and Tax Act.

In the Illinois adult use framework, state residents 21+ may possess up to 30 grams of cannabis flower, 500 milligrams of cannabis in THC-infused products, or 5 grams of cannabis concentrate. Illinois visitors are able to possess half those amounts. Unlike medical marijuana patients, adult users are not permitted to grow marijuana at home. Within the medical framework a patient may possess up to 2.5 ounces of cannabis  within a 14 day period unless given a waiver by a certifying health care professional. Medical patients are allowed to grow five plants at a time.